This invention relates to a Composite Dart Body having a high weight to volume composite body construction that provides superior performance in several applications, especially in darts. The invention also provides a method for making the improved body construction.
State-of-the-art darts are produced in a wide range of shapes and designs, and are constructed from a number of materials, both metallic and non-metallic. Easily machined materials such as copper-base alloys, particularly various grades of brass, are commonly used to provide a relatively low cost construction, free machining characteristics, adequate resistance to corrosion from the atmosphere and from human contact, and for esthetic appearance.
In some darts of more advanced state-of-the-art, higher density materials such as sintered tungsten-copper alloys have been utilized to produce darts with slimmer or smaller diameter bodies for a given desired weight of dart. These so-called tungsten-copper alloys (or tungsten-nickel, tungsten-copper-nickel, tungsten-nickel-iron, or similar materials) are not true alloys, but can be more correctly described as liquid-phase sintered composites in which the tungsten particles are infiltrated and surrounded by a matrix of copper, nickel, copper-nickel, nickel-iron, or other similar lower melting point binder. Darts have been constructed using bodies of these tungsten heavy metal alloys containing up to a maximum of about 90-95% tungsten content, balance binder metals. More typically, materials such as 70% tungsten and 30% copper and similar tungsten-base materials have been used. These tungsten heavy metals are machinable so they can be drilled and tapped to receive the point of the dart at the front, and the tail feather assembly at the rear of the dart body by means of threaded connections. In some cases, the heavy metal bodies have been bonded by techniques such as adhesive bonding to the point and tail feather assembly to make the complete dart.
These tungsten heavy metal bodies do provide a dart with a generally desired slimmer body for a given desired weight, but since they are produced by sintering, variations in density and a resulting imbalance can occur in the sintered parts because of density variations produced in pressing or molding the original part before sintering, or from density variations resulting from the much higher density of tungsten than of the binder metals. For example, in Military Specification "Tungsten Base, High Density Metal (Sintered or Hot Pressed)", MIL-T-21014B(ASG), Amendment 1, June 9, 1961, Class 1 Material contains approximately 90% tungsten, but the allowable density can range from 16.85 to 17.25 g/cm.sup.3. In addition, the maximum density of such readible machinable heavy metal parts is limited to about 18.3 g/cm.sup.3 maximum.
It is frequently desired in darts to have an asymmetrical location of the center of gravity of the dart body along its length. A dart that is "nose heavy", i.e., which has its center of gravity located toward the front portion of the dart body, has been found to exhibit improved stability in flight, and, consequently, improved accuracy. In state-of-the-art darts where the body is machined from a single material (such as brass, or tungsten heavy metals, as examples), this "nose-heavy" feature is achieved either by: a tapered body shape, with the largest diameter toward the front; or by drilling out material from the rear of the body. In order to achieve the desired weight in such darts, it is necessary to increase the diameter of the dart body. Also, the small diameter ends of types with a tapered body, or the drilled out portion of the end of darts of this type are weakened structurally as a consequence.
In some state-of-the-art darts, a tungsten heavy metal front piece is attached by a threaded connection to a lower density, more readily machinable material such as brass to achieve a "nose-heavy" weight distribution. However, such constructions do not provide as small a diameter body for a given desired dart weight as do the composite dart bodies of this invention.
This invention provides an improved dart body construction produced by using a dart body material with uniform density characteristics throughout the body, and having a density of at least 18.5 g/cm.sup.3 and more particularly, at least 18.9 g/cm.sup.3, and 19.3 g/cm.sup.3 in the preferred embodiment.
One objective of this invention is to provide a dart body utilizing such high density materials that would result in a dart with a substantially diminished size for a given weight, which allows the player to throw more darts into a smaller area of the target.
A further objective is to provide a dart body that will result in less interference for subsequent darts that are thrown by the player, particularly when the earlier darts are not embedded perpendicular to the thrown arc of the darts, thus substantially improving the scoring capabilities.
Another objective is to provide a dart body resulting in improved accuracy of the darts because of their high weight to diameter ratio and weight to length ratio.
Another objective of the invention is to provide a dart with a more durable body construction than dart bodies produced from commonly used machinable materials.
Another objective is to provide a dart body offering a simplicity of assembly.
Still another objective is to provide a composite, unitized dart body construction.
Still another objective is to provide a dart giving improved accuracy because of a completely symmetrical weight distribution in the dart body because of its uniform, high density construction.
A further objective is to provide a dart giving improved accuracy by means of an asymmetrical location of the center of gravity along its length in some embodiments while still maintaining the advantages of a smaller diameter for a given weight of the dart body.
Still another additional objective is to provide a dart body having improved strength and hardness compared with state-of-the-art materials used in darts.
Other objects and features of the invention will be apparent in the following description and claims in which the invention is set forth together with a detailed explanation on how to make the product of the invention in connection with the best mode presently contemplated for the practice of the invention.